P020C: Cylinder 3 Injection Timing
What to do
Ask for all the injectors to be tested rather than just the one named, especially on a high-mileage engine. A leak-back test compares them against each other and shows whether one has failed or the whole set is wearing out — and that changes the repair decision considerably.
Mention any recent injector work and whether calibration codes were programmed in. An injector fitted without its code sets this fault with a perfectly good part.
Say whether the engine is rough from cold, warm, or both. Cold-only roughness points at glow plugs or compression rather than injection timing on that cylinder.
What this code means
Injection timing on cylinder 3 is not where the module commanded it to be.
On a four-cylinder engine this is the third in the firing order, and on a straight six it sits in the middle of the block — a position with its own characteristic problem. The centre cylinders of an inline engine run hottest, because they have cylinders either side of them rather than one side open to coolant flow. Injectors there age faster, and a timing deviation that appears on a middle cylinder first is often the beginning of a set rather than an isolated fault.
That is worth knowing before agreeing to replace one injector. Where the others are the same age and mileage, replacing a single injector on a high-mileage engine frequently buys a few months before the next one declares itself.
The diagnosis is otherwise the family's. The module derives combustion timing from the crankshaft's instantaneous speed, so a cylinder that burns late, burns weakly, or does not burn cleanly all disturb the same measurement. Compression, glow plug and injector each have to be eliminated on that cylinder before the injector is condemned by position alone.
A leak-back test across all injectors is the measurement that settles it, because it compares them against each other rather than against a specification — and a set that is drifting together is a different conversation from one that has failed.
Likely causes
Start here
- Worn or leaking fuel injectors · specialist
- Failed fuel injector · specialist
Less common
- Injector fitted without entering its calibration code · specialist
- Low engine compression · specialist
- Leaking injector seal · specialist
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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What makes one worth reading:
- The car — make, model, year and engine. The same fault behaves differently on each.
- What you measured, not only what you replaced.
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